There is history between geeks and facial hair. See: 1978.
The very first staff photo of Microsoft includes several bearded members totaling 7 out of 9 men, mostly programmers.
And I presume it wasn't 8 out of 9 because young Bill Gates looks incapable of sprouting much at this time. (The talented female programmer on the bottom centre of the photo, Andrea Lewis, was respectfully left out of this count.) Snopes.com explains the photo was used in a email chain that went around asking if people would have invested money with such odd looking folks.
Apple's geeks have had a relationship with their moustaches, too.
Although from an earlier era then when the photograph of mustached Steve was taken, Andy Hertzfeld, early employee, tells a story at folklore.org about the belief that a bushy upper lip was an asset when gunning for a promotion. In It's The Moustache That Matters, Burrell, official a lowly tech, who was so amazing that he was filling in on engineering work for Woz, couldn't get the raise he deserved. Until he grew a 'stache.
It obviously wasn't a matter of talent or technical skill, since he was already far more accomplished in that regard than most of the other hardware engineers. It wasn't a matter of working harder, since Burrell already worked harder and was more productive than most of the others. Finally, he noticed something that most of the other engineers had in common that he was lacking: they all had fairly prominent moustaches. And the engineering managers tended to have even bigger moustaches. Tom Whitney, the engineering VP, had the largest moustache of all.
So Burrell immediately started growing his own moustache. It took around a month or so for it to come in fully, but finally he pronounced it complete. And sure enough, that very afternoon, he was called into Tom Whitney's office and told that he was promoted to "member of technical staff" as a full-fledged engineer.
But facial hair was in style at the end of the 70s, when these companies were being birthed. What about in recent decades?
Modern geeks, like those in the Python beard Flickr group, carry on this tradition. And here's an entire blog post arguing that languages developed by bearded programmers have higher success rates, with plenty of recent examples.
This isn't exactly conclusive evidence that mustaches make for more successful geeks, but it is strange correlation.
Not that it always looks good. I found this post on Deviant art with illustrated advice to geeks on how they can avoid looking like scumbags.
And Jesus Diaz teased me mercilessly for ruining the precious apple prom by arriving unshaven to a town hall event.
There's even a site asking people to try and guess if the photos displayed belong to programmers or serial killers, some of the examples sporting fine facial handlebars. But I don't believe any of us think looking good is the point here.
Being moustachio-ed myself, and putting on the amateur psychologist's hat, I'd say that facial hair could have its appeal in several ways. As a young teen I was always very slight, and had to eat a lot to even fit into regular clothes. One time, my mother, always great at creating embarrassing moments, asked a salesperson at the mall if there were any women's jeans that fit me. With softer, cherubic features, facial hair helped me feel more masculine, even when it was just a weak sliver. Now, as I round 30, it just works in a different direction. That is, to hide face and neck fat. I guess facial hair just makes the ugly, better. Or at least hides it. Or makes it hairier. Now, don't get me wrong. I think geeks are beautiful on the inside, but there aren't as many geek supermodels as there are ones with mustaches.
Unkempt, long facial hair on geeks might also signal an obsessive tendency to ignore everything but whatever a geek is geeking out on, whether that be blogging, designing, engineering, programming or making, at the sacrifice of haircuts, shaves, and showers. Although not necessarily in his moustache phase, early Apple employees complained about Steve Jobs' hygiene, finally getting someone to mention that he needed to bathe more often.
But I could be reading into this a bit much. And as I can only speak for myself, in the end, I'll stick with the theory that, I probably just want to be like Mario.